1. Field of the Invention
The present invention relates to an improved curved electrode which is used for a resistance welding apparatus, for example.
2. Description of the Background Art
Conventionally, in an apparatus for resistance welding such as spot welding or the like, an electrode having a curved shape is used due to the shape of a material to be welded. As for the electrode having a curved shape, if the offset amount is too large, excessive moment is applied to the installing portion of the electrode due to an applied load at the time of welding. In this case, if the installing portion is fixed by taper engagement, the tapered hole is deformed into an elliptical shape, thus, it cannot be used. Therefore, there has been known a technique in which the vicinity of the installing portion of the electrode is retained by a cap nut (See Japanese Patent Application Publication No. 7-60458.
In the conventional curved electrode 51, as shown in FIG. 6, an installing portion 51a to be installed in an electrode holder or the like, an offset portion 51b by which the offset amount is obtained, and a tip portion 51c which comes into contact with a material to be welded are formed unitarily. Therefore, it takes a lot of time to manufacture, and the cost is high. Also, when the tip portion 51c is worn, the entire device needs to be replaced, which increases the maintenance cost. Additionally, in a case where a cooling passage is formed into the curved electrode 51, although a linear cooling passage such as that shown by a broken line in FIG. 6 can be formed in the installing portion 51a, it is difficult to extend the cooling passage toward the offset portion 51b and the tip portion 51c. Therefore, the electrode easily suffers from heat damage, and its durability is poor.
An object of the present invention is to provide a curved electrode which can be manufactured easily at a low cost, and replaced at a low cost in a case where a part of it is damaged, and in which the durability can be improved at the same time.